type b1 = { name: string; age: number; skill: string };
type PICK<T, U extends keyof T> = {
  // 原生 Pick已经实现了
  // keyof T 等价于 name | age | skill
  [P in U]: T[P];
};

type b2 = PICK<b1, "name" | "age">;
// type b2 = Pick<b1, "name" | "age">;
const b3: b2 = {
  name: "",
  age: 0,
};
export default {};
